Conventionally, personal identification is performed by comparing veins and finger prints with feature point extraction data obtained by the minutia method (for example, Patent Document 1).
The feature point extraction method is generally considered invulnerable to rotation or displacement. In reality, however, when rotation or displacement actually occurs, the feature point extraction method has a problem that the brightness of an image changes so greatly that important feature points are lost in many cases.
In addition, the brightness of the image also changes greatly due to scattered light or indirect reflection light of the sunlight, or due to change in the amount of blood flow depending on an outdoor air temperature. As a result, feature points at a finger joint and an edge portion of the finger are lost, and thereby the authentication score decreases.    Patent Document 1: Japanese Patent Application Publication No. 2001-243465.